A variety of articles, for example, packaging materials (for example, containers, wrapping paper, trays, tubes, bags, and pouches) as well as structures, textiles, and toys, are known as articles whose surface has been endowed with water repellency and oil repellency. The packaging materials are used with, for example, foods, beverages, medicines, cosmetics, and chemicals, such as jelly confections, puddings, yogurts, liquid cleansers and detergents, toothpastes, curry roux, syrups, petroleum jellies, facial cleansing creams, and facial cleansing mousse. In addition, the content can have various forms, such as solid, semisolid, liquid, viscous material and gel. Water repellency or oil repellency is imparted, in conformity with the nature of the content, to the surface in contact with the content in order to prevent attachment of the content to the greatest extent possible.
For example, methods in which coating is carried out with, e.g., a fluorinated compound, are used as a means for imparting water repellency and oil repellency.
For example, the oilproof packaging material disclosed in Patent Document 1 is made by laminating at least the following three layers in the indicated sequence: (A) a thermoplastic resin layer in which upper surface pores (x) having a pore diameter of 0.2 to 0.6 mm have been executed in advance; (B) an oilproof paper that incorporates an oilproofing agent in which the number of carbons in the perfluoroalkyl group is less than 8; and (C) a heat-sealable thermoplastic resin layer in which back surface pores (y) having a pore diameter of 0.2 to 0.6 mm have been executed in advance.
Patent Document 2 provides a water- and oil-repellent base material that characteristically comprises the following first layer formed on a surface of a base material and the following second layer formed on the surface of the first layer: for the first layer, a silica fine particle-containing layer of the cured product from a curable paint; for the second layer, a layer formed from a composition in which the essential components are a fluorosilicone compound and a solvent, or a layer formed from the cured product of such a composition.
Patent Document 3 discloses a packaging material for a deoxygenating agent, an ethanol pervaporation agent, or a desiccant for preserving the freshness of food. This packaging material is characterized by a two-layer coating provided by first coating the surface on at least one side of an air-permeable paper base material with a urethane-type or vinyl chloride acetate-type transparent ink that uses an isocyanate-type curing agent and then applying a fluorine-type water- and oil-repellent agent on this urethane-type or vinyl chloride acetate-type transparent ink layer.
With regard to the art of coating with such fluorinated compounds, methods have also been introduced in which coating is carried out with a liquid dispersion that contains fine particles and an oil-repellent agent.
For example, a method of producing an oil-repellent coated article is disclosed in Patent Document 4, wherein this method characteristically comprises (1) a first step in which fine particles having a particle diameter of at least 100 nm are produced by the sol-gel method and (i) an article to be coated is immersed in a liquid dispersion in which the fine particles are dispersed and is withdrawn and dried or (ii) a liquid dispersion in which the fine particles are dispersed is sprayed on the article to be coated and drying is carried out; and (2) a second step in which (i) the article to be coated is then immersed in a liquid dispersion that contains fine particles with a particle diameter of 7 to 90 nm and a perfluoroalkylsilane as an oil-repellent agent and is withdrawn and dried or (ii) the article to be coated is sprayed with a liquid dispersion containing fine particles with a particle diameter of 7 to 90 nm and an oil-repellent agent and drying is carried out.
There is disclosed in Patent Document 5 a water- and oil-repellent coated article that is a coated article obtained by the application of a coating composition that contains alcohol, an alkoxysilane, a perfluoroalkylsilane, silica fine particles, a catalyst that promotes the hydrolysis reaction of alkoxysilanes, and water, wherein the root-mean-square roughness (RMS) value for the surface of this coated article is at least 100 nm.
Patent Document 1: Japanese Patent Application Publication No. 2011-73744
Patent Document 2: Japanese Patent Application Publication No. 2000-169835
Patent Document 3: Japanese Patent Application Publication No. 2009-191407
Patent Document 4: Japanese Patent Application Publication No. 2011-140625
Patent Document 5: Japanese Patent Application Publication No. 2010-89373
However, while the art described in these patent documents does achieve a certain degree of water repellency or oil repellency, in order to promote a more practical implementation the adoption is still necessary of a method than can more reliably realize a satisfactory water repellency and oil repellency.